SB 210396 is an active & selective primatized monoclonal antibody directed at a CD4 antigenic determinant of a known structure. This compound has already demonstrated safety in pts. w/rheumatoid arthritis at doses from .03 to 4.0 mg/kg. Clinical activity was observed w/single doses of .12 to 1 mg/kg. By transiently decreasing the number & activity of CD4 positive lymphocytes, SB 210396 may improve the clinical outcomes in asthma via a reduction in the inflammatory events.